1. Field of the Invention
The purpose of this invention is to control and optimize the performance parameters of switchable holograms to tailor the properties to application-specific devices.
2. Description of the Related Art
U.S. Pat. No. 5,942,157 provides a description of materials and methods for producing switchable holographic Bragg gratings.
U.S. Pat. Nos. 5,751,452 and 5,748,272 to Tanaka et al. teach an optical device made from a switchable holographic polymer dispersed liquid crystal (hereafter “PDLC”) grating and methods for fabricating the same. Tanaka et al. teach the use of NOA65 (polyene and polythiol mixture), but do not teach how it may be used in conjunction with a multifunctional acrylate to reduce switching voltage and eliminate voltage creep. In their teaching, NOA65 is the sole polymerizable monomer in the described embodiments. These embodiments are also found in U.S. Pat. Nos. 4,938,568 and 5,096,282 to Margerum et al.
U.S. Pat. No. 5,875,012, and European Patent Application Nos. 98300541.1, 98300543.0, and 98300468.0 to Crawford et al. teach reflective displays made with switchable PDLC holograms, but provide little in the way of materials or methods for optimizing performance. Crawford et al. teach the use of an anisotropic polymer index-matched to the liquid crystal to reduce haze at large viewing angles. This is also taught in U.S. Pat. Nos. 4,994,204 and 5,240,636 Doane et al. U.S. Pat. No. 5,731,853 to Taketomi et al. and U.S. Pat. No. 6,083,575 Ninomiya et al. teach devices made with switchable PDLC holograms, but provide no teaching for optimizing switchable hologram performance.
U.S. Pat. No. 5,313,317 to Saburi et al. and U.S. Pat. Nos. 5,330,264 and 5,648,857 to Ando et al. teach beam control methods for controlling unwanted gratings (i.e., “ghost holograms”) in non-PDLC holograms using particular geometrical arrangements.
Each of the above-identified references is incorporated by reference herein in its entirety.